Method for disseminating geolocation information for network infrastructure devices

ABSTRACT

A scheme is provided for distributing reference geographical locations on a network. Geolocation information is integrated or associated with one or more network infrastructure devices to permit them to serve as reference points for the rest of the network. A reference geographical location associated with a network infrastructure device may be broadcast by the network infrastructure device over a network. Alternatively, other network devices may request reference geographical location from a network infrastructure device or obtain it from a network-accessible database that stores such geolocation information. Other network devices can then use the one or more reference geographical locations to determine their own geographical location. By allowing existing network devices to take advantage of the geolocation capability of its “neighboring” network devices, this scheme provides a convenient way to deliver geolocation to many network devices.

REFERENCE TO CO-PENDING APPLICATIONS FOR PATENT

The present Application for Patent is related to the followingco-pending U.S. Patent Application: “Geo-Locating End-User Devices on aCommunication Network” by Liren Chen, et al., having Ser. No.11/483,268, filed concurrently herewith, assigned to the assigneehereof, and expressly incorporated by reference herein.

BACKGROUND

1. Field

Various embodiments pertain to network devices, and more specifically tonetwork infrastructure devices with knowledge of their own geographicallocation and a protocol that facilitates distribution of thisgeographical information to other network devices to facilitategeolocation on a network.

2. Background

The advent of IP-based networks has spawned many applications, includingservices that rely on, or benefit from, knowledge of geographicallocation information of network devices. However, the nature of IPnetworks makes it difficult to geographically locate devices on thenetwork. That is, the geographical transparency of IP networks, wheredevices are identified by an IP address not location, makes it verydifficult to identify the geographical location of network devices withany precision. This poses a problem when deploying services that relyon, or benefit from, knowing the geographical location of a networkdevice. For example, voice-over-IP (VOIP) telephone communicationservices rely on knowing the geographical information of a telephonedevice to route emergency calls. An emergency call cannot be easilyrouted to a nearby call center without knowing the geographical locationof the telephone device. In the event that the caller using a VOIPtelephone is unable to provide an address, emergency services may beunable to locate the caller in any other way. Regulations of telephoneservices impose the need to locate a telephone device for emergencypurposes.

Implementing geolocation support by including a global positioningdevice in each user network device, such as VOIP telephones, typicallyresults in higher purchase costs for the user devices and, possibly,additional monthly service charges. Moreover, geolocation systems likeGPS will typically not work well indoors where most phones are used.Alternatively, a preset or user-entered geographical location might beconsidered, but, since a network device may be moved to a differentgeographical location and reconnected to an IP network as part of normaluse this method of geolocation for the network device is unreliable andimpractical.

Thus, a way is needed to facilitate geolocation support for networkdevices on a communication network.

SUMMARY

A method is provided for disseminating geolocation information betweennetwork infrastructure devices. A geographical location of a referencenetwork device is obtained and stored as part of the managementinformation base of the reference network device. The geographicallocation may then be provided to other network devices on thecommunication network. Changes in the geographical location of thereference network device are also monitored and the geographicallocation is updated if the reference network device moves. The referencenetwork device may be authorized to provide its geographical location toother network devices on the communication network.

The geographical location may be represented as a longitude and alatitude and may be automatically propagated to other network devices. Anetwork time protocol that facilitates distance estimation betweennetwork devices by synchronizing their clocks may be supported. Anexpiration timestamp may be appended to the geographical locationprovided to other network devices, wherein the expiration timestampindicates how long the geographical location can be relied on.

The geographical location of the reference network device may be (a)obtained from an onboard global positioning device, (b) a manuallyconfigured into the reference network device, or (c) derived by usingother geographical locations for other reference network devices. In thecase of (c) above, the geographical location of the reference networkdevice may be obtained by (1) acquiring one or more referencegeographical locations for other reference network devices, (2)determining one or more distances from the reference network device toeach of the one or more reference geographical locations, and then (3)deriving the geographical location of the reference network device basedon the one or more reference geographical locations of the otherreference network devices and the one or more distances. The one or morereference geographical locations may be obtained from a root referenceserver on the communication network.

An accuracy indicator may be associated with the geographical locationof the reference network device. This accuracy indicator may be providedalong with the geographical location of the reference network device.The accuracy indicator may be determined based on one or more accuracyindicators associated with one or more reference geographical locationsfor other reference network devices. When updating the geographicallocation of the reference network device based on one or more newreference geographical locations for other reference network deviceshaving associated accuracy indicators, the reference network device usesa particular reference geographical location only if its associatedaccuracy indicator is better than the accuracy indicator associated withthe reference network device.

Another feature provides for (1) obtaining a reference geographicallocation associated with a second reference network device, (2)synchronizing a first clock in the reference network device with asecond clock in the second reference network device, the synchronizedfirst and second clocks facilitating a direct one-way trip timemeasurement between the reference infrastructure device and the secondreference network device, (3) obtaining a one-way distance between thereference infrastructure device and the second reference network devicebased on the direct on-way trip time measurement, and (4) obtaining thegeographical location associated with the reference network device basedon the reference geographical location and the one-way distance. Thedirect one-way trip time measurement is performed for both a transmitpath from the reference network device and a receive path to thereference network device. The transmit path may have a differenttransmission speed than the receive path.

Another aspect provides for (1) determining the transmission mediumbetween the reference network device and the second reference networkdevice, (2) determining a propagation speed of the transmission medium,(3) obtaining a propagation time between the reference network deviceand the second reference network device based on the transmission mediumpropagation speed between the reference network device and the secondreference network device, and (4) obtaining the geographical locationassociated with the reference network device based on the referencegeographical location and the propagation time.

A network device is also provided having (a) an input interfaceconfigured to obtain a geographical location associated with the networkdevice, (b) a processing circuit coupled to the input interface, and/or(c) an output interface coupled to the processing circuit to transmitthe geographical location over a communication network to other networkdevices. The processing circuit may be configured to (1) obtain thegeographical location from the interface, (2) store the geographicallocation as part of the management information base of the referencenetwork device, (3) automatically propagate the geographical informationto other network devices via the output interface, and/or (4) monitorfor changes in the geographical location of the network device. Theinput interface may be coupled to one of either: an internal geolocationdevice, an external geolocation device, or a user input device formanual entry of geolocation information.

The input interface may be a local interface to couple directly to areference infrastructure device to obtain a reference geographicallocation. In some implementations, the network infrastructure deviceknows the transmission medium to the reference infrastructure device anda propagation speed of the transmission medium. The transmission mediumpropagation speed is used to obtain a propagation time to the referenceinfrastructure device and the geographical location associated with thenetwork infrastructure device is obtained based on the referencegeographical location and the propagation time to the referenceinfrastructure device. The network infrastructure device may alsoinclude first clock to synchronize with a second clock in the referenceinfrastructure device. The synchronized first and second clocksfacilitating a direct one-way trip time measurement between the networkinfrastructure device and the reference infrastructure device. Thedirect one-way trip time measurement is performed for both a transmitpath from the network infrastructure device and a receive path to thenetwork infrastructure device.

Yet another embodiment provides a machine-readable medium having one ormore instructions for enabling a network device to facilitatepropagation of geolocation information on a communication network, whichwhen executed by a processor causes the processor to: (a) obtain areference geographical location associated with a second networkinfrastructure device, (b) synchronize a first clock in the networkinfrastructure device with a second clock in the second networkinfrastructure device, the synchronized first and second clocksfacilitating a direct one-way trip time measurement between the networkinfrastructure device and the second network infrastructure device, (c)obtain a one-way distance between the network infrastructure device andthe second network infrastructure device based on the direct on-way triptime measurement, (d) obtain a geographical location associated with thenetwork infrastructure device based on the reference geographicallocation and the one-way distance, and (e) provide the geographicallocation to a third network device on the communication network toenable the third network device to obtain its own geographical location.

Yet another feature provides a method for disseminating geolocationinformation across a network, comprising: (a) providing a referencegeographical location from a reference network infrastructure device toother network infrastructure devices on the network, (b) synchronizingclocks between the reference network device and a first networkinfrastructure device to facilitate a one-way trip time measurementbetween the reference network infrastructure device and the firstnetwork infrastructure device, (c) obtaining a distance between thereference network device and the first network infrastructure devicebased on the one-way trip time measurement, and (d) obtaining ageographical location for the first network infrastructure device basedon the reference geographical location and the distance between thereference network device and the first network infrastructure device.The method may compensate for time delays caused be intervening networkdevices between the reference network device and the first networkinfrastructure device to enhance the accuracy of the distance betweenthe reference network infrastructure device and the first networkinfrastructure device. Additionally, the method may include the steps of(a) obtaining a roundtrip time measurement between the reference networkinfrastructure device and a non-synchronized network infrastructuredevice, (b) ascertaining processing delays at the non-synchronizednetwork infrastructure device, (c) obtaining a distance between thereference network device and the non-synchronized network infrastructuredevice based on the roundtrip time measurement and compensating for theprocessing delays, and (d) obtaining a geographical location for thenon-synchronized network infrastructure device based on the referencegeographical location and the distance between the reference networkdevice and the non-synchronized network infrastructure device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a network in which one or more referenceinfrastructure devices include geolocation information that enablesother network devices to determine their own geographical location.

FIG. 2 illustrates a network infrastructure device having a geolocationconfiguration interface that enables it to obtain its geographiclocation and distribute it to other devices on a network.

FIG. 3 illustrates a method for providing reference geolocationinformation to a network infrastructure device.

FIG. 4 illustrates a network device configured to determine ageographical location based on geographic information obtained from oneor more network infrastructure devices.

FIG. 5 illustrates a method for a first network device to determine itsown geographical location based on reference geographical locations ofone or more reference network infrastructure device on the network.

FIG. 6 is a diagram illustrating how the geographic location of a firstnetwork device may be determined based on the known geographic locationsof other network devices.

FIGS. 7 and 8 illustrate other methods for disseminating geolocationinformation across a network.

FIG. 9 illustrates an alternative geolocation infrastructure device.

DETAILED DESCRIPTION

In the following description, specific details are given to provide athorough understanding of the embodiments. However, it will beunderstood by one of ordinary skill in the art that the embodiments maybe practiced without these specific details. For example, circuits maynot be shown in block diagrams in order not to obscure the embodimentsin unnecessary detail.

Also, it is noted that the embodiments may be described as a processthat is depicted as a flowchart, a flow diagram, a structure diagram, ora block diagram. Although a flowchart may describe the operations as asequential process, many of the operations can be performed in parallelor concurrently. In addition, the order of the operations may bere-arranged. A process is terminated when its operations are completed.A process may correspond to a method, a function, a procedure, asubroutine, a subprogram, etc. When a process corresponds to a function,its termination corresponds to a return of the function to the callingfunction or the main function.

Moreover, a storage medium may represent one or more devices for storingdata, including read-only memory (ROM), random access memory (RAM),magnetic disk storage mediums, optical storage mediums, flash memorydevices, and/or other machine readable mediums for storing information.The term “machine readable medium” includes, but is not limited toportable or fixed storage devices, optical storage devices, wirelesschannels, and various other mediums capable of storing, containing, orcarrying instruction(s) and/or data.

Furthermore, embodiments may be implemented by hardware, software,firmware, middleware, microcode, or a combination thereof. Whenimplemented in software, firmware, middleware, or microcode, the programcode or code segments to perform the necessary tasks may be stored in amachine-readable medium such as a storage medium or other storage means.A processor may perform the necessary tasks. A code segment mayrepresent a procedure, a function, a subprogram, a program, a routine, asubroutine, a module, a software package, a class, or a combination ofinstructions, data structures, or program statements. A code segment maybe coupled to another code segment or a hardware circuit by passingand/or receiving information, data, arguments, parameters, or memorycontents. Information, arguments, parameters, data, and the like, may bepassed, forwarded, or transmitted via a suitable means including memorysharing, message passing, token passing, and network transmission, amongothers.

Introduction

One feature provides a network of reference infrastructure devices withknown geographical locations that facilitate geolocating other networkdevices. The reference infrastructure devices serve as geographicalreference points and propagate their geographical locations to be usedfor geolocation by other network devices. In various implementations,the reference infrastructure devices have highly accurate geographicallocations provided by manual configuration, an onboard geolocationdevice (e.g., GPS), or other means. Additionally, a networkinfrastructure device may ascertain its own geographical location byobtaining the location of one or more neighboring referenceinfrastructure devices and the distance(s) to the one or moreneighboring reference infrastructure devices.

Reference geographical location information may be propagated through adata or communication network in various ways that allow other networkdevices to obtain their own geographical location. A referencegeographical location may be broadcasted or distributed by a referenceinfrastructure device or requested by other network devices.Additionally, the reference geographical locations may be stored and/ormaintained by one or more databases that network devices can access tofacilitate geolocation. Existing network devices may take advantage ofthe geographical locations of “neighboring” reference infrastructuredevices to ascertain their own geographical locations.

Geolocation Dissemination Scheme Generally

FIG. 1 illustrates a network in which one or more referenceinfrastructure devices include geolocation information that enablesother network devices to determine their own geographical location. Thenetwork may include a plurality of reference infrastructure devices A102, B 104, C 106, E 110, and F 112, each of which may becommunicatively coupled to other network devices. Since most networkinfrastructure devices, including routers, servers, modems, hubs andswitches, rarely move, they are ideal candidates to be used asgeographical reference points in order to enable geolocation of othernetwork devices. In some implementations, infrastructure devices A 102,B 104, C 106, and F 112 may obtain their geographical location via anintegrated or external geolocation device, such as a GPS device, or froma manually-entered geographical configuration. By deploying referencegeolocation information only on the network infrastructure devices, thecost of deploying geolocation on a network is reduced. In otherinstances, the infrastructure devices may, instead, be manuallyconfigured with a geographical location. This is particularly effectivewhere a network infrastructure device is rarely moved or if its positionis properly maintained. These geographical locations may then serve asreference geographical points for other network devices 108, 110, and114.

Infrastructure Device with Internally Generated or Stored GeolocationInformation

Some network infrastructure devices may store their referencegeographical locations internally (e.g., in the network device). In someimplementations, the reference geographical locations may also be storedby an external database that stores IP addresses of networkinfrastructure devices and their corresponding geographical locations.This may permit other network devices to obtain one or more storedgeographical locations based on IP addresses.

Infrastructure Device with Externally Obtained Geolocation Information

According to one feature, a network infrastructure device E 110 notequipped with an internal/external geolocation device or a userconfigured/entered geographical location may determine its owngeographical location based on the reference geographical locations ofone or more other infrastructure devices A 102, B 104, C 106, and/or F112. That is, infrastructure device E 110 may receive broadcasts from,or query, infrastructure devices A 102 and F 112, for example, to obtaintwo reference geographical locations. It can then determine thedistances to each infrastructure device A 102 and F 112 in various ways.As described with reference to FIG. 6, distance determination betweentwo infrastructure devices may be in various ways. Once distances toinfrastructure devices A 102 and F 112 are determined, infrastructuredevice 110 can use these and the corresponding reference geographicallocations to obtain its own geographical location.

Geolocation Propagation Schemes Generally

A protocol may be established on the network that permits networkinfrastructure devices A 102, B 104, C 106, E 110, and F 112 topropagate their geographical location to other network devices orprovide it upon request. In one implementation, network device 202broadcasts its geographical location to the network periodically and/orupon the occurrence of an event (e.g., new geographical information isdetected, etc.). In other implementations, network device 202 sends itsgeographical information to a requesting network device. According toone example, the geographical information of a plurality of networkdevices may be stored in a network database, along with identifyinginformation (e.g., IP address) for the corresponding network device.This enables a network device seeking geolocation to obtain referencegeographical locations with which to determine its own geographicallocation.

Passive Reception of Broadcast Information

A network infrastructure device that already knows its currentgeographical location may provide this reference geographical locationby broadcasting it on the network. For example, network infrastructuredevices A 102, B 104, C 106, E 110, and F 112 may broadcast theirgeolocation information along with a device identifier (e.g., device ID,IP address, media access control ID, etc.). The network infrastructuredevices may broadcast this information periodically, based on aschedule, and/or when their geographical location information changes.Neighboring network devices passively receive such broadcasts and usethe geolocation information therein to determine their own geographicallocations.

Active Discovery

An active discovery mechanism may also be provided by which a networkdevice may identify the local network infrastructure devices that canserve as geolocation reference points. Network infrastructure devices A102, B 104, C 106, E 110, and F 112 may disseminate their currentgeographical location to other network devices by responding to a queryor request for such information. This may be done by a network devicequerying or otherwise obtaining identifying information from“neighboring” reference network infrastructure devices. Once one or morenetwork infrastructure devices are identified, a network device mayobtain or request geolocation information from the identified networkinfrastructure devices. For instance, since most network devices supportremote monitoring protocols, such as the Simple Network ManagementProtocol (SNMP), the geographical location of a particular networkinfrastructure device can be obtained by other network devices havingaccess privileges to such information. For example, the IP address of anetwork infrastructure device (having a reference geographical location)may be used to query its geographical location from its managementinformation base (MIB). Alternatively, network infrastructure devicesmay respond to specific requests for their geolocation information fromother network devices.

Geolocation Expiration Timestamp

One feature also enables a reference network infrastructure device tocontrol the length of time that its' broadcasted or distributedgeolocation information should be used by receiving network devices.This feature gives a network infrastructure device control of how longits geographical location is good for. This may be achieved by appendingan expiration timestamp or date to the reference geographic locationdistributed by the network infrastructure device. In this example, it isassumed that the reference network infrastructure device is in the bestposition to determine how often it changes locations and set theexpiration timestamp accordingly. Network devices receiving thisreference geographical location information and expiration timestamprely on the reference geographical location for the period defined bythe expiration timestamp and stops using it after that. The referencenetwork infrastructure device can update its geolocation information toaccount for movements. Expiration timestamps also help avoid the use ofinvalid/outdated geographical locations by network devices.

Authorization of Reference Infrastructure Devices

Yet another aspect provides a mechanism to identify and authenticateinfrastructure devices that are sending or requesting geolocationinformation. For this purpose, an infrastructure device may beprovisioned with an identifier, authorization key, and/or unique key(e.g., either from a management server 118, self-generated or manuallyconfigured). In one implementation, this permits other network devicesto determine whether the geolocation information received from anotherinfrastructure device should be considered a valid referencegeographical location. In another implementation, a reference networkdevice may encrypt the geolocation information being broadcasted usingits' keys to avoid unauthorized eavesdropping. In yet anotherimplementation, an infrastructure device may not be allowed to broadcastor disseminate its geolocation information to other devices unless it isauthorized to do so. The management server 118 may authorize one or moreinfrastructure devices A 102, B 102, C 106, E 110, and/or F 112 to actas reference infrastructure devices and allow them to broadcast ordisseminate their geographical locations.

Root Reference Server

In yet another implementation, geolocation information may bedisseminated to infrastructure device or network devices via a rootreference server 116. For example, the root reference server 116 mayoperate as a central database of reference infrastructure devices orreference geographical information. Network devices may be configured tocontact the root reference server 116 to obtain geolocation information(e.g., network infrastructure device identifiers and/or their associatedgeographical locations).

In one implementation, root reference server 116 provides referencegeographical locations of “neighboring” network infrastructure devicesfrom which a network device, including a network infrastructure device,can determine its own geographical location. That is, networkinfrastructure devices without onboard or configured geographicallocations may determine their geographical locations by obtaining one ormore reference geographical points from root reference server 116 anddetermining the distances to the infrastructure devices associated withthe reference geographical points.

In other implementations, the root reference server 116 may be used as areference geographical location itself. This permits a network device touse the location of root reference server 116 (and possibly other rootreference servers) and determine a distance to the root reference server116 to obtain its geographical location.

Stratum Propagation

The source and/or accuracy of reference geographical locations may be afactor in deciding which network infrastructure devices A 102, B 104, C106, E 110, and F 112 to use as geographical reference points.Preferably, these reference geographical locations have the highestlevel of accuracy (e.g., stratum 0). However, in some implementations, ageographical location may be derived from a combination of referencegeographical locations having different levels of accuracy (e.g.,stratums 0, 1, 2, 3, etc.).

As a general rule, reference geographical locations of higher accuracyand/or reliability are preferred over less accurate or reliablegeographical locations. In addition, reference network infrastructuredevices that have been configured with highly accurate geographicalinformation (e.g., a specifically surveyed geographical location) arepreferred over other reference network infrastructure devices havingless precise or reliable geographical information (e.g., GPS-basedgeographical data or geographical information derived from otherneighboring devices, etc.). Thus, geolocation information from networkinfrastructure devices having more accurate position information arepreferred over other network infrastructure devices that may have lessaccurate geographical locations. For this purpose, networkinfrastructure devices may provide the accuracy of their geographicalinformation (e.g., stratum 0, 1, 2, etc.) when disseminating thegeographical information. Generally, stratum 0 indicates the highestlevel of accuracy/confidence with increasing stratums being lessaccurate.

A “stratum” may act as an indicator of how may hops a particular networkinfrastructure device is from a source device having originalgeolocation information (e.g., obtained from an attached GPS device ormanually configured). A network device that derives its geographicallocation from a second network device automatically increments itsstratum level from the stratum level of the second network device.Source network devices may start with different stratum levels based onthe quality of their geolocation location information (e.g. GPS, survey,map estimation, etc.) and all geolocation derivations have associatedstratum levels that go up from that reference stratum level. Thisprovides a simple method for managing stratum numbers and preventslooping by only using geolocation information having an associatedstratum level equal or lower than its own stratum level.

A network infrastructure device A 102, B 104, C 106, E 110, or F 112and/or its geographical location information may be associated with alevel of accuracy (e.g., stratum 0, 1, 2, etc.) based on the accuracy ofits geographical location information (e.g., the source of thegeographical information, the number of physical hops from the actualsource of the geographical information, etc.). For example, networkinfrastructure devices A 102, B 104, C 106, and F 112 may be categorizedas stratum 0 devices (e.g., having the highest level of accuracy).Network infrastructure device E 110 may be an infrastructure device thatderives its geographical location based on reference geographicallocations from network infrastructure devices A 102 and F 112, bothstratum 0 devices, thus network device E 110 is stratum 1. Similarly,other network infrastructure devices may be categorized as stratum 2, 3,etc., based on the relative accuracy of the source of their geolocationinformation. The specific categorization of a geographical location asstratum 0, 1, 2, etc., may vary depending on the particular geolocationscheme employed, the relative accuracy of the geographical location,etc. For example, as discussed above, the stratum level of a networkdevice may be obtained by incrementing by one the stratum level of itssource for geolocation information.

Anti-Looping of Stratums

One feature of the accuracy indicator provides an anti-looping mechanismthat prevents network infrastructure devices (as well as regular networkdevices) from updating their geographical locations based on lessaccurate reference geolocation information. Since a networkinfrastructure device (or regular network device) knows the accuracy ofits own geographical location information (based on the associatedstratum level), it can avoid updating it based on a newly received orupdated reference geographical point of less accuracy (e.g., having ahigher stratum level). For example, if a network device having stratum 1accuracy receives a new reference geographical location of stratum 2accuracy, it should ignore the new reference geographical location. Inone implementation, a network device may only update its geolocationinformation based on reference geolocation information having a lowerassociated stratum level.

Infrastructure Device Hardware

FIG. 2 illustrates a network infrastructure device having a geolocationconfiguration interface that enables it to obtain its geographiclocation and distribute it to other devices on a network. Networkinfrastructure device 202 may include a processing unit 204 coupled to acommunication interface 206 and a geolocation configuration interface208. Communication interface 206 may serve to couple networkinfrastructure device 202 to a data and/or communication network. Insome implementations, geolocation configuration interface 208 may be anintegrated or external GPS device that provides a current or livegeographical location to network infrastructure device 202. In otherinstances, geolocation configuration interface 208 may be a userinterface or device interface that permits manually configuring thegeographical location of network infrastructure device 202. For example,a geographical survey may be performed to obtain an accurategeographical location which is then configured into the network devicevia geolocation configuration interface 208. In some implementations,the geolocation information may be integrated with or stored as part ofthe management information base (MIB) of network infrastructure device202.

Processing unit 204 may be configured to receive geolocation informationfrom geolocation configuration interface 208 and store it and/or deliverit to other network devices. Optionally, processing unit 204 may alsosend or provide the level of accuracy, reliability, and/or confidence ofthe geographical location stored by network infrastructure device 202.

Method for Operating Network Infrastructure Device

FIG. 3 illustrates a method for providing reference geolocationinformation to a network infrastructure device. A network infrastructuredevice is provisioned with an interface to obtain geographical locationinformation 302. Such interface may enable the network infrastructuredevice to obtain its geographical location 304. For example, an internalor external device may be coupled to the interface and serve as a sourceof geographical position information or the interface may allow manuallyentry of this geographical information. The geographical information maybe stored as part of a management information base of the networkinfrastructure device 306. The geographical location is then provided toother network devices 308. In various implementations, the geographicallocation may be propagated to other network devices via broadcasts, as areply to an information request from a particular network device, or viaone or more databases that maintain the geographical locations ofnetwork devices. This geographical information may enable implementationof particular types of geographically-dependent services over thenetwork. The geographical location of the network infrastructure devicemay be monitored 310 to determine whether there has been a change 312.If there is a change, the new geographical location is obtained 304 andthe process is repeated.

Network Device

FIG. 4 illustrates a network device configured to determine ageographical location based on geographic information obtained from oneor more network infrastructure devices. In some implementations, networkdevice 402 may be a network infrastructure device that has no onboardgeolocation capabilities or configured geographical location. Networkdevice 402 includes a processing unit 404 coupled to a communicationinterface 406 and a storage unit 408 (e.g., memory, etc.). Communicationinterface 406 may communicatively couple network device 402 to a dataand/or communication network.

In one implementation, network device 402 is configured to determine itsown geographical location by obtaining one or more referencegeographical locations from network infrastructure devices (e.g., viareceived broadcasts, specific requests, or via a root reference server),then determining the distance to those network infrastructure devices,and triangulating its position based on this information. To identifynetwork infrastructure devices that can serve as reference geographicallocations, network device 402 may broadcast a request for networkinfrastructure devices to send or broadcast their geographical location.For example, neighboring network infrastructure devices within N hops(where N is an integer number) of the requesting network device mayprovide their geographical location. Alternatively, network device 402listen for geolocation broadcasts from neighboring networkinfrastructure devices. In yet another implementation, network device402 may contact a pre-defined root reference server from which it canobtain reference geolocation information or contact information for“neighboring” reference network infrastructure devices from which it canobtain reference geolocation information. Once one or more geographicallocations are obtained, network device 402 can resolve the distances tothe responding network infrastructure devices and determine its owngeographical location.

Method for Operating Network Device

FIG. 5 illustrates a method for a first network device to determine itsown geographical location based on reference geographical locations ofone or more reference network infrastructure device on the network. Thefirst network device may obtain reference location information fromsurrounding or nearby network infrastructure devices. Thus, a referencenetwork infrastructure device in a data and/or communication network isidentified 502. This may be done, for instance, by using a route traceutility to identify network infrastructure devices within N hops (whereN is an integer value). Alternatively, the first network device maytransmit a request for all reference network infrastructure deviceswithin N network hops to provide their geolocation information. In yetanother example, the first network device may listen to broadcasts ofsuch reference geographical information from network infrastructuredevices and store them for later use. Another example provides one ormore databases (e.g., root reference servers) on the network that storegeolocation information for reference network infrastructure devices andprovide this information to other network devices. In this manner, areference geographical location associated with the reference networkinfrastructure device 504 is obtained. Typically, the first networkdevice preferably obtains geolocation information from a locallyconnected neighbor since more accurate data can be used to make thegeolocation calculation. Two network devices are said to be locallyconnected (in Internet Protocol (IP) networking terminology), if the twonetwork devices have no Layer 3 IP devices on the path between them.Otherwise their connection is considered “remote”.

A distance from the first network device to reference networkinfrastructure device 506 is then determined. This may be done inseveral ways. For example, where a network time protocol is supported onthe network, the clocks on network devices are synchronized andtransmitted packets are time stamped. Using the transmit and receivetimes for packets between two network devices, the one-way delay timebetween them can be ascertained. Since most network infrastructuredevices know the interface transmission speed and the type of medium(which determines the transmission medium propagation speed) for theircommunication interfaces, the propagation time between the two localnetwork devices can be measured directly by removing the transmissiontime. If two network devices have a remote connection, the propagationtime between them may be measured indirectly and a transmission mediumpropagation speed may be estimated. Knowing the propagation time andtransmission medium propagation speed, the distance between the twonetwork devices is then ascertainable. If synchronized clocks are notavailable on the network devices, then propagation time can still beestimated by taking measurements of round-trip delay times and using thelocal clock to record transmit and receive times and dividing by two toascertain the one-way delay time. Then the rest of the operations canproceed as outline above for local or remote connections as appropriate.

A geographical location for the first network device can then bedetermined based on the reference geographical location and distance tothe reference network infrastructure device 508, taking into account the“stratum” level of their position accuracy. This calculated geographicallocation is then stored 510 in the first network device and may beprovided to requesting network devices 516 with the appropriate derivedaccuracy indicated.

If other reference network infrastructure devices are available alongdifferent network paths 512, this process is repeated to obtain two ormore geographical locations for the network device. These two or moregeographical locations are then triangulated to obtain a more accurategeographical location for the first network device 514.

In one implementation, the method illustrated in FIG. 5 may be performedby a network device to obtain its own geographical location. In anotherimplementation, the method illustrated in FIG. 5 is implemented by anetwork device to find the geographical location of other networkdevices on a communication network.

Infrastructure Device Location Determination Scheme

FIG. 6 is a diagram illustrating how the geographic location of a firstnetwork device may be determined based on the known geographic locationsof other network devices. In one example, the geographical locations ofnetwork infrastructure devices A 604, B 606, and C 608 are known andused as reference geographical locations by other network devices. Someof these network infrastructure devices may obtain their geographicallocations from onboard GPS devices or manually configured locations anddisseminate or broadcast their geographical locations over the network.Meanwhile, other participating network infrastructure devices may nothave onboard GPS devices or manually configured locations but insteadobtain their geographical locations by based on the known geographicallocation of neighboring network infrastructure devices and the distanceto those devices. The distance between two network infrastructuredevices may be determined based on the propagation time and transmissionmedium propagation speed along a path between the two networkinfrastructure devices. That is, the distance between two networkinfrastructure devices may be defined as the transmission mediumpropagation speed (v_(propagation)) times propagation timet_(propagation). The distance determination between two networkinfrastructure devices may be done either “locally” or “remotely”.

Local Distance Determination

Local distance determination can be performed when the networkinfrastructure devices are locally connected (by IP network definition)and are aware of the medium type and transmission medium propagationspeed between the network infrastructure devices. In particular, inlocal distance determination the network infrastructure device is ableto readily determine a propagation time t_(propagation) and transmissionmedium propagation speed v_(propagation).

Participating network infrastructure devices may support clocksynchronization, for example, by employing a Network Time Protocol (NTP)that synchronizes the clocks of network infrastructure devices overpacket-switched networks. For instance, a first network infrastructuredevice A 604 and a second network infrastructure device 606 B may havesynchronized clocks. By appending a transmit timestamp to a transmittedpacket from the first network infrastructure device A 604 to the secondnetwork infrastructure device B 606, second network infrastructuredevice B 606 is able to ascertain the one-way trip time of the packetacross the local link 624. That is, when the packet is received by thesecond network infrastructure device B 606 a receive timestamp iscreated. By subtracting the transmit timestamp from the receivetimestamp, the overall one-way trip time t_(trip) is obtained. The triptime t_(trip) is defined as the sum of a transmission timet_(transmission) and a propagation time t_(propagation). Consequently,the propagation time t_(propagation) ist _(propagation) =t _(trip) −t _(transmission)A network infrastructure device can obtain the transmission timet_(transmission) for a received packet based on its known interfacetransmission speed v_(transmission) and the received packet size P1. Inparticulart _(transmission) =P1/v _(transmission)Thus the propagation time,t _(propagation) =t _(trip) —P1/v _(transmission)can be ascertained, locally, by receiving network infrastructure deviceB 606. Most network infrastructure devices (e.g., Layer 3 networkdevices), such as routers, have knowledge of the physical transmissionmedium through which they are connected to a data or communicationnetwork or other infrastructure devices. For example, networkinfrastructure device B 606 may be a Layer 3 device that knows thetransmission medium of path 624 through which it communicates withinfrastructure device A 604. The transmission medium may be fiber optic,coaxial cable, etc., for example. In some instances, networkinfrastructure device B 606 may infer the transmission medium based onits interface transmission speed v_(transmission). Knowing thetransmission medium, a network infrastructure device can then obtain atransmission medium propagation speed v_(propagation). For example,Table 1 defines known propagation speed v_(propagation) for differenttransmission mediums that a network infrastructure device may use.

TABLE 1 Transmission Medium Propagation Speed Thick Coaxial .77 c(231,000 km/sec) Thin Coaxial .65 c (195,000 km/sec) Twisted Pair Copper.59 c (177,000 km/sec) Fiber Optic .66 c (198,000 km/sec) AUI Cable .65c (195,000 km/sec)Having obtained a propagation time t_(propagation) and transmissionmedium propagation speed v_(propagation) over path 624, networkinfrastructure device B 606 can determine the distance to networkinfrastructure device A 604.

Additionally, making measurements with synchronized clocks allows thenetwork infrastructure devices to make measurements of both the transmitand receive links between the network infrastructure devices. The samemethod described above can be applied to both sides of the path (e.g.,transmit and receive) for cases where the physical link may haveasymmetric bandwidth such as a cable modem or DSL links. Computation ofthe two propagation time measurements allows both pieces of data to beinput into the geolocation determination process to increase accuracy.Generally, the shorter calculated distance is the more accuratemeasurement of the distance between the two network infrastructuredevices.

For locally connected network infrastructure devices that do not havesynchronized clocks, the local distance determination method may bemodified to allow one network device to send a ping packet which recordsthe round trip time (e.g., based on transmit and receive timestamps)between the two network devices via the clock on the network device thatsends and receives the ping. Then the one-way trip time is obtained bydividing the measured round trip time by two.

Remote Distance Determination

Remote distance determination provides an alternative approach to localdistance determination. Remote distance determination is performed whentwo network infrastructure devices have a remote IP connection. If thetwo network devices do not have synchronized clocks, then the followingoperation reviewed below is used. This method is covered in theco-pending U.S. Patent Application: “Geo-Locating End-User Devices on aCommunication Network” by Liren Chen, et al.

In remote distance determination without synchronized clocks, thedistance to a reference infrastructure device may be ascertained byusing network pings. For example, a network infrastructure device C 608may attempt to determine its geographic location based on the referencegeographical location of network infrastructure device A 604. Separateroundtrip time measurements (e.g., pings) t1_(roundtrip) andt2_(roundtrip) are done by network infrastructure device C 608 over path626 to network infrastructure device A 604 using different packet sizesP1 and P2. These time measurements may be accomplished, for example, byusing a high-resolution pinging utility (e.g., having a resolution of 1microsecond). The roundtrip time measurements maybe performed in closeproximity in time so as to minimize the effects of varying networktraffic or loads, and processing loads.

Roundtrip ping time t1_(roundtrip) is defined ast1_(transmission)+t1_(propagation), and a round-trip ping timet2_(roundtrip) is defined as t2_(transmission)+t2_(propagation). Thepropagation time is directly related to the transmission mediumpropagation speed of the electromagnetic signal across the physicalmedium of the path 626 and how far the signal has to travel. It isindependent of the measuring packet size P1 or P2. Therefore, for thesame path 626, t1_(propagation) equals t2_(propagation), referred tohereafter as t_(propagation). This means that transmission times (e.g.,t1_(transmission) and t2_(transmission)) are determined by the size ofthe packet (e.g., P1 and P2) being transferred, divided by the bandwidthof the transmission path 626 times 2 (packet is sent twice). Often, thebandwidth is relatively stable when ping measurements are taken in closeproximity in time. Therefore,t1_(roundtrip)=2*(P1/path_bandwidth)+t _(propagation)t2_(roundtrip)=2*(P2/path_bandwidth)+t _(propagation).The path_bandwidth can then be calculated as the difference betweenpacket sizes P2 and P1 divided by the difference in roundtrip ping timest2_(roundtrip) and t1_(roundtrip) times two (2) such that:path_bandwidth=2*(P2−P1)/(t2_(roundtrip) −t1_(roundtrip)).The roundtrip propagation time t_(propagation) of path 626 can then becalculated as the difference between an overall path roundtrip time andthe roundtrip transmission time, such that:t _(propagation) =t _(roundtrip) —t _(transmission), ort _(propagation) =t _(roundtrip) —P1×((t2_(roundtrip) —t_(roundtrip))/(P2−P1)),where P1 and P2 are different packet sizes sent between the two networkinfrastructure devices, and t1_(roundtrip) and t2_(roundtrip) are therespective roundtrip times for the packet sizes P1 and P2. Consequently,the one-way propagation time is given ast _(one-way propagation) =t _(propagation)/2.

A nominal transmission medium propagation speed v_(propagation) for thepath 626 transmission medium is then selected. Electromagnetic signalspropagate at a constant speed on a transmission medium. Since thetransmission medium of the path 626 may be characterized using the pathbandwidth, a transmission medium propagation speed v_(propagation) maybe selected as the nominal transmission medium propagation speed for thepath 626 based on the best characterization of the transmission medium.That is, depending on the determined path bandwidth, the path 626 may becharacterized as twisted pair copper wire, coaxial cable, fiber optic,etc., and a transmission medium propagation speed v_(propagation) basedon that medium can then be used. Table 1 defines known transmissionmedium propagation speeds v_(propagation) for different transmissionmediums that a network infrastructure device may use.

The one-way distance of the path 626 can then be determined as:distance=v _(propagation) ×t _(one-way propagation)where v_(propagation) is the transmission medium propagation speed forthe path 626 and t_(one-way propagation) is the one-way propagation timeacross path 626. In some implementations, multiple roundtrip timemeasurements are obtained and the smallest propagation timet_(one-way propagation) is used to determine the distance betweennetwork infrastructure devices 604 and 608.

When clocks are synchronized between two network devices, then the abovemethod is modified to measure the one-way trip times directly instead ofmeasuring the round-trip time and dividing it by two to estimate theone-way trip time. That is, a path_bandwidth is determined in bothtransmit and receive directions (from the point of reference of thefirst network device that is attempting its own geolocationdetermination) denoted by path_bandwith_(T) and path_bandwidth_(R). Thenone-way propagation times, t_(one-way propagationR) andt_(one-way propagationT) can be computed (divide by two step from aboveis omitted) from the path_bandwith_(T) and path_bandwidth_(R). These twopropagation times can now both be used as input to the geolocationdetermination process for better accuracy.

Intervening Network Devices

In some implementations a receiving network device, such as a Layer 3router or other device, is able to use the information (e.g., a transmittimestamp, a physical medium type, interface transmission speed,queueing delay, link utilization, etc.) from a transmitting networkinfrastructure device and, possibly, intervening network devices, thatmay be sent in a network protocol packet, to help estimate the actualpropagation time. From this information, a distance between thetransmitting and receiving device may be determined more accurately.

Specifically, in the case of remote distance determination between twonetwork devices where their clocks are unsynchronized, the receivingnetwork device could include a processing time estimate in the pingpacket that is to be sent back to the first network device performingthe geolocation operation. Including the estimate of processing time bythe receiver on the ping packet allows the calculation of realpropagation time to be more accurate and thus the distance estimate maybe more accurate. That is, round-trip time can more completely bewritten ast _(roundtrip) =t _(transmission) +t _(propagation) +t _(processing)And t_(processing) can be included in the return packet by the receivingnetwork device to allow the transmitting network device to remove thattime when calculating the estimated t_(propagation.)

This protocol may be extended to enable Layer 2 devices (e.g., networkswitches, etc.) to share their information (e.g., interface transmissionspeed, physical medium type, and possibly other information likeestimated processing time, estimated queueing delay, link utilization,etc.), as well. That is, an intervening Layer 2 network device mayappend its information to a distance determination packet sent betweentwo Layer 3 network devices, the receiving network device may be able todetermine the delay caused by the intervening Layer 2 device and itsassociated links. By accounting for delays of intervening Layer 2network devices and links, a Layer 3 network device may be able to moreaccurately determines its distance to another Layer 3 network device.

Location Triangulation

Network infrastructure devices may also be configured to use multiplereference geographical locations to more accurately determine their owngeographical location. For any single distance measurement, a networkinfrastructure device D 602 may be located within a radius of referencenetwork device A 604 along a perimeter region 610. To further narrow itslocation, multiple reference geographical locations are used to definemultiple perimeter regions 610, 612, and 614. From these multipleperimeter regions, a more accurate geographical location can beascertained from the intersection or overlap of two or more perimeterregions 610, 612, and 614. Such intersection or overlap location may bedetermined from triangulation of the reference geographical locations(e.g., for network infrastructure devices A, B, and C) and the distancesto the network infrastructure device D 602 along transmission paths 616,620, and 624.

One or more of the components, steps, and/or functions illustrated inFIGS. 1, 2, 3, 4, 5 and/or 6 may be rearranged and/or combined into asingle component, step, or function or embodied in several components,steps, or functions without departing from the invention. Additionalelements, components, steps, and/or functions may also be added withoutdeparting from the invention. The apparatus, devices, and/or componentsillustrated in FIGS. 1, 2, 4 and/or 6 may be configured to perform oneor more of the methods, features, or steps described in FIGS. 3 and/or5. For example, FIGS. 7 and 8 illustrate other methods for disseminatinggeolocation information across a network while FIG. 9 illustrates analternative geolocation infrastructure device.

In FIG. 7, a reference geographical location associated with a referencenetwork infrastructure device is provided to other networkinfrastructure devices on a network 702. Clocks between the referencenetwork device and a first network infrastructure device aresynchronized to facilitate a one-way trip time measurement between thereference network infrastructure device and the first networkinfrastructure device 704. A distance between the reference networkdevice and the first network infrastructure device is obtained based onthe one-way trip time measurement 706. A geographical location for thefirst network infrastructure device is obtained based on the referencegeographical location and the distance between the reference networkdevice and the first network infrastructure device 708. The method mayalso compensate for time delays caused be intervening network devicesbetween the reference network device and the first networkinfrastructure device to enhance the accuracy of the distance betweenthe reference network infrastructure device and the first networkinfrastructure device 710.

In FIG. 8, a roundtrip time measurement is obtained between a referencenetwork infrastructure device and a non-synchronized networkinfrastructure device 802. Processing delays at the non-synchronizednetwork infrastructure device are ascertained 804. A distance betweenthe reference network device and the non-synchronized networkinfrastructure device is obtained based on the roundtrip timemeasurement and compensating for the processing delays 806. Ageographical location for the non-synchronized network infrastructuredevice is obtained based on the reference geographical location and thedistance between the reference network device and the non-synchronizednetwork infrastructure device 808.

FIG. 9 illustrates a network infrastructure device 902 including ageolocation acquisition module 904 for obtaining the geographicallocation of the network infrastructure device, a storage device 906 forstoring the geographical location of the network infrastructure device902, and a communication interface 908 for providing the geographicallocation of the network infrastructure device 902 to other networkdevices. Additionally, the network infrastructure device may include amonitoring module 910 for monitoring for a change in the geographicallocation of the network infrastructure device 902.

Accordingly, a network infrastructure device may comprise means forobtaining the geographical location of the network infrastructuredevice, means for storing the geographical location of the networkinfrastructure device, means for providing the geographical location ofthe network infrastructure device to other network devices, and/or meansfor monitoring for a change in the geographical location of the networkinfrastructure device.

Those of skill would further appreciate that the various illustrativelogical blocks, modules, circuits, and algorithm steps described inconnection with the embodiments disclosed herein may be implemented aselectronic hardware, computer software, or combinations of both. Toclearly illustrate this interchangeability of hardware and software,various illustrative components, blocks, modules, circuits, and stepshave been described above generally in terms of their functionality.Whether such functionality is implemented as hardware or softwaredepends upon the particular application and design constraints imposedon the overall system.

It should be noted that the foregoing embodiments are merely examplesand are not to be construed as limiting the invention. The descriptionof the embodiments is intended to be illustrative, and not to limit thescope of the claims. As such, the present teachings can be readilyapplied to other types of apparatuses and many alternatives,modifications, and variations will be apparent to those skilled in theart.

1. A method for disseminating geographical location information betweennetwork devices, comprising: obtaining a geographical location of areference network device; storing the geographical location; andsupporting a network time protocol that facilitates distance estimationbetween the reference network device and one or more other networkdevices by synchronizing their clocks; wherein the geographical locationis provided to at least one of the one or more other network devices fordetermining a geographical location of the at least one of the one ormore other network devices using packet exchanges based on the clocksynchronization; and wherein a mechanism is provided to selectivelyidentify and authenticate at least one network device as beingauthorized to act as the reference network device to the at least one ofthe one or more other network devices.
 2. The method of claim 1, furthercomprising: monitoring for a change in the geographical location of thereference network device and updating the geographical location when themonitoring indicates a change in the geographical location of thereference network device.
 3. The method of claim 1, wherein thegeographical location includes a longitude and a latitude.
 4. The methodof claim 1, wherein the geographical location is automaticallypropagated to the one or more other network devices.
 5. The method ofclaim 1, wherein the geographical location of the reference networkdevice is obtained from an onboard global positioning device.
 6. Themethod of claim 1, wherein the geographical location of the referencenetwork device is manually configured into the reference network device.7. The method of claim 1, wherein the geographical location of thereference network device is obtained by: acquiring one or more referencegeographical locations for other reference network devices; determiningone or more distances from the reference network device to each of theone or more reference geographical locations; and deriving thegeographical location of the reference network device based on the oneor more reference geographical locations of the other reference networkdevices and the one or more distances.
 8. The method of claim 7, whereinthe one or more reference geographical locations are obtained from aroot reference server on the network.
 9. The method of claim 1, furthercomprising: including an indication of a level of accuracy of thegeographical location in the geographical location of the referencenetwork device, wherein the level of accuracy indicates a number of hopson the communication network that the reference network device islocated from a source device with a geographic location informationhaving a highest level of accuracy; and providing the level of accuracyindication along with the geographical location.
 10. The method of claim9, wherein the level of accuracy indication is determined based on oneor more level of accuracy indications associated with one or morereference geographical locations for other reference network devices.11. The method of claim 9, further comprising: updating the geographicallocation of the reference network device using only one or more otherreference network device with a geographical location having a level ofaccuracy indication indicating an equal or greater accuracy than thelevel of accuracy of the reference network device.
 12. The method ofclaim 1, further comprising: appending an expiration timestamp to thegeographical location provided to the at least one of the one or moreother network devices, wherein the expiration timestamp indicates howlong the geographical location can be relied on.
 13. The method of claim1, wherein the mechanism further authorizes the reference network deviceto provide its geographical location to the at least one of the one ormore other network devices.
 14. The method of claim 1, wherein thegeographical location of the reference network device is obtained by:obtaining a reference geographical location associated with a secondreference network device; synchronizing a first clock in the referencenetwork device with a second clock in the second reference networkdevice, the synchronized first and second clocks facilitating a directone-way trip time measurement between the reference network device andthe second reference network device; obtaining a one-way distancebetween the reference network device and the second reference networkdevice based on the direct one-way trip time measurement; and obtainingthe geographical location associated with the reference network devicebased on the reference geographical location and the one-way distance.15. The method of claim 14, wherein the direct one-way trip timemeasurement is performed for both a transmit path from the referencenetwork device and a receive path to the reference network device, and aone-way distance between the reference infrastructure network device andthe second reference network device based on the direct one-way triptime measurement is determined for each of the transmit path and thereceive path, the shorter of the one way distance of the transmit pathand the receive path is employed to obtain the geographical location.16. The method of claim 15, wherein the transmit path has a differenttransmission speed than the receive path.
 17. The method of claim 14,further comprising: determining the transmission medium between thereference network device and the second reference network device;determining a propagation speed of the transmission medium; obtaining apropagation time between the reference network device and the secondreference network device based on the transmission medium propagationspeed between the reference network device and the second referencenetwork device; and obtaining the geographical location associated withthe reference network device based on the reference geographicallocation and the propagation time.
 18. The method of claim 1, whereinthe one or more other network devices are restricted to network devicespositioned within a threshold number of network hops to the referencenetwork device.
 19. The method of claim 1, wherein a mechanism isprovided to selectively identify and authenticate the at least one ofthe one or more other network devices as being authorized to request thegeographical location.
 20. The method of claim 1, wherein the mechanismselectively identifies and authenticates at least one network device asbeing authorized to act as the reference network device to all of theone or more other network devices.
 21. The method of claim 1, whereinthe mechanism comprises one or more of an authorization key or a uniquekey, or combinations thereof.
 22. The method of claim 1, wherein thereference network device operates within a transmission line basedcommunication network, and wherein the geographical location is providedto the at least one of the one or more other network devices on thetransmission line based communication network.
 23. The method of claim1, wherein the geographical information is stored as part of amanagement information base of the reference network device.
 24. Anetwork device comprising: an input interface configured to obtain ageographical location associated with the network device; a processingcircuit coupled to the input interface and configured to obtain thegeographical location from the interface, store the geographicallocation and support a network time protocol that facilitates distanceestimation between the reference network device and one or more othernetwork devices by synchronizing their clocks; and an output interfacecoupled to the processing circuit to transmit the geographical locationto at least one of the one or more other network devices for determininga geographical location of the at least one of the one or more othernetwork devices using packet exchanges based on the clocksynchronization, wherein a mechanism is provided to selectively identifyand authenticate the network device as being authorized to act as areference network device to the at least one of the one or more othernetwork devices.
 25. The network device of claim 24, wherein theprocessing circuit is further configured to automatically propagate thegeographical information to the at least one of the one or more othernetwork devices via the output interface.
 26. The network device ofclaim 24, wherein the processing circuit is further configured tomonitor for changes in the geographical location of the network device.27. The network device of claim 24, wherein the input interface iscoupled to one of either an internal geolocation device, an externalgeolocation device, or a user input device for manual entry ofgeolocation information.
 28. The network device of claim 24, wherein thegeographical location of the network device is obtained by: acquiringone or more reference geographical locations for other network referencedevices; determining one or more distances from the network device toeach of the other network reference devices; and deriving thegeographical location of the network device based on the one or morereference geographical locations of the other network reference devicesand the one or more distances.
 29. The network device of claim 24,wherein the input interface is a local interface to couple directly to areference infrastructure device to obtain a reference geographicallocation.
 30. The network device of claim 29, wherein a transmissionmedium to the reference infrastructure device and a propagation speed ofthe transmission medium are determined.
 31. The network infrastructuredevice of claim 30, wherein the transmission medium propagation speed isused to obtain a propagation time to the reference infrastructure deviceand the geographical location associated with the network device isobtained based on the reference geographical location and thepropagation time to the reference infrastructure device.
 32. The networkdevice of claim 29, further comprising: a first clock to synchronizewith a second clock in the reference infrastructure device, thesynchronized first and second clocks facilitating a direct one-way triptime measurement between the network device and the referenceinfrastructure device.
 33. The network device of claim 32, wherein thedirect one-way trip time measurement is performed for both a transmitpath from the network device and a receive path to the network device.34. The network infrastructure device of claim 33, wherein the transmitpath has a different transmission speed than the receive path.
 35. Thenetwork device of claim 24, wherein the processing circuit is furtherconfigured to: include an indication of a level of accuracy of thegeographical location in the geographical location of the referencenetwork device, wherein the level of accuracy indicates a number of hopson the communication network that the reference network device islocated from a source device with a geographic location informationhaving a highest level of accuracy; and transmit the level of accuracyof the geographical location along with the geographical location. 36.An apparatus, comprising: means for obtaining a geographical location ofa reference network device; means for storing the geographical location;and means for supporting a network time protocol that facilitatesdistance estimation between the reference network device and one or moreother network devices by synchronizing their clocks; and wherein thegeographical location is provided to at least one of the one or moreother network devices for determining a geographical location of the atleast one of the one or more other network devices using packetexchanges based on the clock synchronization; and wherein a mechanism isprovided to selectively identify and authenticate at least one networkdevice as being authorized to act as the reference network device to theat least one of the one or more other network devices.
 37. The apparatusof claim 36, further comprising: means for monitoring for a change inthe geographical location of the reference network device.
 38. Anon-transitory machine-readable storage medium having one or moreinstructions for enabling a network device to facilitate propagation ofgeographical location information, which when executed by a processorcauses the processor to: obtain a reference geographical locationassociated with a second network device; synchronize a first clock inthe network device with a second clock in the second network device, thesynchronized first and second clocks facilitating a direct one-way triptime measurement between the network device and the second networkdevice; obtain a one-way distance between the network device and thesecond network device based on the direct one-way trip time measurementusing packet exchanges; obtain a geographical location associated withthe network device based on the reference geographical location and theone-way distance; and provide the geographical location to a thirdnetwork device to enable the third network device to obtain its owngeographical location, wherein a mechanism is provided to selectivelyidentify and authenticate the network device as being authorized to actas a reference network device to the third network device.
 39. Thenon-transitory machine-readable storage medium of claim 38, furthercomprising one or more instructions to: acquire one or more referencegeographical locations for other network infrastructure devices;determine one or more distances from the network device to each of theone or more reference geographical locations; and derive thegeographical location of the network device based on the one or morereference geographical locations of the other network devices and theone or more distances.
 40. The non-transitory machine-readable storagemedium of claim 38, further comprising one or more instructions beingfurther executable by the processor to: include an indication of a levelof accuracy of the geographical location in the geographical location,wherein the level of accuracy indicates a number of hops on thecommunication network that the reference network device is located froma source device with a geographic location information having a highestlevel of accuracy; and provide the level of accuracy of the geographicallocation along with the geographical location.
 41. The non-transitorymachine-readable storage medium of claim 40, wherein the level ofaccuracy of the geographical location is determined based on one or morelevel of accuracy associated with one or more reference geographicallocations for other network devices.
 42. The non-transitorymachine-readable storage medium of claim 40, further comprising one ormore instructions to update the geographical location of the networkdevice based on one or more new reference geographical locations forother network devices having associated level of accuracy, wherein thenetwork device uses a particular reference geographical location only ifits associated level of accuracy is better than the level of accuracyassociated with the network device.
 43. The non-transitorymachine-readable storage medium of claim 38, further comprising one ormore instructions to append an expiration timestamp to the geographicallocation provided to other network devices, wherein the expirationtimestamp indicates how long the geographical location can be relied on.44. A method for disseminating geographical location information acrossa communication network, comprising: providing a reference geographicallocation from a reference network device to other network devices,wherein a mechanism is provided to identify and authenticate at a firstnetwork device of the other network devices as being authorized torequest the reference geographical location; synchronizing clocksbetween the reference network device and the first network device tofacilitate a one-way trip time measurement between the reference networkdevice and the first network device; obtaining a distance between thereference network device and the first network device based on theone-way trip time measurement using packet exchanges occurring over thetransmission lines; and obtaining a geographical location for the firstnetwork device based on the reference geographical location and thedistance between the reference network device and the first networkdevice.
 45. The method of claim 44, further comprising: compensating fortime delays caused by intervening network devices between the referencenetwork device and the first network device to enhance the accuracy ofthe distance between the reference network device and the first networkdevice.
 46. The method of claim 44, further comprising: obtaining aroundtrip time measurement between the reference network device and anon-synchronized network infrastructure device; ascertaining processingdelays at the non-synchronized network infrastructure device; obtaininga distance between the reference network device and the non-synchronizednetwork infrastructure device based on the roundtrip time measurementand compensating for the processing delays; and obtaining a geographicallocation for the non-synchronized network infrastructure device based onthe reference geographical location and the distance between thereference network device and the non-synchronized network infrastructuredevice.
 47. A non-transitory machine-readable storage medium having oneor more instructions which when executed by a processor causes theprocessor to: obtain a geographical location of a reference networkdevice; store the geographical location; and support a network timeprotocol that facilitates distance estimation between the referencenetwork device and one or more other network devices by synchronizingtheir clocks; wherein the geographical location is provided to at leastone of the one or more other network devices for determining ageographical location of the at least one of the one or more othernetwork devices using packet exchanges based on the clocksynchronization; and wherein a mechanism is provided to selectivelyidentify and authenticate at least one network device as beingauthorized to act as the reference network device to the at least one ofthe one or more other network devices.